Light emitting semiconductors are well known in the prior art. One of the more widely used light emitting devices is a heterojunction light emitter fabricated, for example, using a gallium arsenide/aluminum gallium arsenide material system. In such devices, a pair of relatively wide band gap layers (aluminum gallium arsenide) of opposite conductivity type are sandwiched around an active region (gallium arsenide). The interfaces between the active region and the wide band gap layers form a pair of heterojunctions. These heterojunctions effectively provide both carrier and optical confinement. The devices are generally used as light emitting diodes or lasers and may be energized using an electrical current or by optical pumping.
An improved light emitting device is described in co-pending U.S. patent application Ser. No. 209,240 of N. Holonyak and assigned to the same assignee as this application. Therein is described a light emitting device wherein the active region comprises one or more layers of gallium arsenide separated by aluminum arsenide barrier layers. The aluminum arsenide binary layers replace previously employed aluminum gallium arsenide ternary barrier layers for the reason that the latter ternary layers have been found to be inherently disordered and to exhibit alloy clustering in the regions adjacent to the gallium arsenide/aluminum gallium arsenide interface. That clustering leads to the device requiring larger threshold currents and exhibiting lower efficiencies. The disclosure and teachings of the aforementioned patent application are incorporated herein by reference.
Light emitting devices such as those described above are generally, although not necessarily, grown by metalorganic chemical vapor deposition ("MO-CVD"), which is described, for example, in a publication entitled "Chemical Vapor Deposition for New Material Applications", appearing in the June, 1978, issue of "Electronic Packaging and Production". Such devices are also grown by molecular beam epitaxy, liquid phase epitaxy, or other suitable deposition techniques. The MO-CVD and MBE processes are generally the preferred ones.
In all of the aforementioned processes, the light emitting devices are produced in wafer form, which wafer is then cleaved or cut to produce individual light-emitting diodes or lasers. This is in contrast to the well-known integrated circuit technology wherein large numbers of active devices are constructed and interconnected on a single chip. Such integration, heretofore, has been unavailable, on a practical basis, for the above-mentioned light emitting semiconductor devices. Attempts to integrate light emitting devices have generally been rather crude--involving the actual physical emplacement of light-emitting structures in etched-out substrates. Such a structure is shown in U.S. Pat. No. 4,165,474 to D. J. Myers.
It is clear that an economic method of integrating heterojunction light emitting devices into larger scale integrated circuits would be an important contribution to the expansion of optical data processing and data communications.
Accordingly, it is an object of this invention to provide a method which enables the integration of III-V compound heterojunction devices into an overall integrated structure.
It is another object of this invention to provide a method for constructing integrated opto-electronic devices which method is both simple and fits with present semiconductor processing technology.